Does it matter if you wash your hands in cold water or hot water? what is more effective?

Warm temperatures: Bacteria, in general, grows in a wide range of temperatures. Mesophilic bacteria grow best in lukewarm to cool warm temperatures, or 77 to 113 degrees f. Thermophilic bacteria grow best in warm to hot temperatures, or 122 to 158 degrees f. Hyperthermophilic bacteria will grow in very hot temperatures, or 158 to 230 degrees f.